A. Field of the Invention
The present invention relates to manipulator apparatus and more particularly to a programmable automatic manipulator system which may be programmed to perform a desired series of operations in succession during repetitive work cycles. The program may be modified during the work cycles by an operator to correct or adjust certain positional steps and operations.
B. Description of the Prior Art
Programmable manipulators have been employed in various industries for some time to transport articles from one location to another and to perform certain pattern operations such as welding, paint spraying or the like. Such programmable manipulators are shown, for example, in Devol U.S. Pat. No. 3,306,471 dated Feb. 28, 1967; Devol U.S. Pat. No. 3,543,947 dated Dec. 1, 1970; Dunne, et al. U.S. Pat. No. 3,661,051 dated May 9, 1972; Engelberger, et al. U.S. Pat. No. 3,744,032 dated July 3, 1973; Engelberger, et al. U.S. Pat. No. 3,885,295 dated May 27, 1975; Devol, et al. U.S. Pat. No. 3,890,552 dated June 17, 1975; British Pat. No. 781,465 and copending application Ser. No. 625,932 cross-referenced above. While these programmable manipulators are generally suitable for their intended purpose, the various devices are not capable of modifying their stored programs during operation such as during a work cycle.
In some applications, the manipulator is programmed for movement to follow a work piece on a moving conveyor and executes a predetermined pattern of operations such as welding, for example, on each work piece as it moves past the manipulator station. In other applications, the manipulator may perform similar patterns of operations or repetitive work cycles on a stationary work piece. In either case, the manipulator is initially programmed during a teaching operation to establish the various desired positions during a work cycle wherein the desired positions are then recorded into memory. The programming or teaching with a moving conveyor may be performed by successively stopping the work piece at different closely spaced locations along the conveyor path, successively moving the manipulator to different positions and recording these positions as discussed in the above reference U.S. Pat. No. 3,744,032. The manipulator is then operated in a repeat mode to perform the repetitive work cycles. The manipulator, when operating with a moving conveyor, tracks an encoder depicting conveyor movement and moves from one programmed step to the next successive step according to the conveyor encoder.
From observation of the operating manipulator, in stationary or conveyor operation, the programmer-operator may detect that welds, for example, are not being performed in precisely the desired locations or a part being inserted or assembled is not being inserted to the desired depth or in the desired position. Also, in a moving conveyor situation, the operator may observe that the manipulator is not at the correct position according to the relative conveyor position. The reasons for the above misalignments or undesirable conditions are numerous and, for example, may have been caused by imperfect initial programming, slight shifts in the orientation of the work piece relative to the manipulator, wearing of manipulator tip or hand apparatus, part variations of the work piece assembly, replacement of dies or small positional changes in handling or delivery apparatus.
The positional misalignments or desired changes in the program steps may be very slight such as a few millimeters and may involve only one or two axes in one program step. Nevertheless, the manipulators of the prior art require that the work cycle and production line be stopped while the manipulator is reprogrammed and repositioned by further steps in the teach mode. This "down-time" or line stoppage in most applications is usually not convenient and many times both impractical and prohibitive economically.